Optimization of thermal neutron flux in an irradiator assembly with different isotopic sources

This work aimed to determine the distribution of thermal neutron flux in an irradiator assembly to study
the possibility of use this irradiator for Neutron Activation Analysis; NAA. To establish the facility
specifications, the thermal neutron flux values of 252Cf and Pu-Be isotopic neutron sources along the
horizontal irradiator axis were determined experimentally and calculated by Monte Carlo N-Particle;
MCNPtransport code. The irradiator assembly characterized by supplying a stable neutron flux for a long
period, eliminating the need to use standard material i.e. comparative method, so that the process
becomes efficient, compact, economical and more reliable. The measurements were carried out at differ
ent position inside the irradiator assembly using proportional 3He-detector and gold foil activation
method. As well as, these measurements were performed without and with two types of neutron reflec
tor such as water and steel to determine the thermal neutron distribution along the irradiation points.
The experimental results were compared to the calculations performed with MCNP Code. The calculated
and experimental results were in reasonable agreement for both 252Cf and Pu-Be sources. This indicated
that the material and geometrical properties of the irradiator were modeled well.